Deuterated precursors (SiD4, ND3) were used for plasma enhanced chemical vapor deposition of thin SiNX passivation layers on both n-GaN and n-GaAs rectifiers. The two main plasma parameters that were found to degrade rectifier performance were gas flow rate ratio (SiD4/ND3) and plasma power. Larger increases in reverse breakdown voltage were observed for the GaN rectifiers compared to the GaAs diodes. The use of the deuterated precursors did not appear to reduce device degradation relative to conventional hydrogenated chemicals. (C) 2002 Published by Elsevier Science Ltd.